Code of Practice for Precast Concrete Contruction 2016 · This Code, Code of Practice for Precast Concrete Construction 2016 (the 2016 Code) is issued upon completion of the review

Code of Practice for

Precast Concrete Construction

Code of Practice

FOREWORD

The Buildings Department established the Technical Committee on the Code of Practice for Precast Concrete Construction (TC) in March 2012 for the purpose of collecting views and feedbacks on the use of the Code of Practice for Precast Concrete Construction 2003 (the 2003 Code) from the building industry and with a view to keeping the Code of Practice in pace with the advancement in design technology and construction practice

This Code Code of Practice for Precast Concrete Construction 2016 (the 2016 Code) is issued upon completion of the review by the TC which has focused on four fronts (a) the advancement in design and technology (b) the experience gained and the views and feedbacks received on the use of the 2003 Code (c) the commonly adopted local practice on precast concrete construction and (d) necessary updates consequent upon the publication of the Code of Practice for Structural Use of Concrete 2013 the issue of Practice Notes for Authorized Persons Registered Structural Engineers and Registered Geotechnical Engineers APP-143 and the issue of Construction Standard CS12010 and CS22012

The contributions and efforts given by the invited members of the Technical Committee in the preparation of the 2016 Code are greatly appreciated

This Code of Practice will be reviewed regularly The Buildings Department welcomes suggestions for improving the Code

First Issue April 2016

CONTENTS

1 General1

11 Scope 1

12 Definitions 1

13 Symbols 2

2 Design 3

21 Scope 3

211 General 3 212 Standards and codes of practice 3

22 Planning 3

221 Standardisation 3 222 Buildability 3 223 Voids and buried conduits 3 224 Layout plan 3 225 Compatibility 4 226 Demolition 4

23 Stability 4

231 General 4 232 Displacement 4 233 Disproportionate collapse 4

24 Durability 5

241 General 5 242 Shape of precast unit 5 243 Concrete cover 5 244 Protection and maintenance of joints and connections 5 245 Movement 6 246 Thermal gradient 6 247 Other effects 6

25 Loadings 6

251 General 6 252 Demoulding forces 6 253 Handling and transportation 7

26 Materials 7

261 General 7 262 Alkali-aggregate reaction 7 263 Chlorides in concrete 8

27 Design considerations 8

271 General 8 272 Handling stresses 8 273 Early lifting of precast element 9 274 Temporary stageserection sequence 9 275 Lifting inserts 9 276 Bracing design 10 277 Design for movement 10 278 Design of ties 11 279 Design of bearings 14

28 Joints and connections 18

281 Structural connections 18 282 Joints 20

29 Composite concrete construction 26

291 General 26

210 Non-structural elements 28

211 Ductility 28

2111 Construction incorporating precast concrete 28 2112 Connections in equivalent monolithic systems 28

3 Construction 29

31 Production planning 29

32 Moulds 29

321 Materials 29 322 Tolerances 29 323 Recesses sleeves and boxouts 30 324 Mould release agents 30

33 Cast-in connections 30

34 Lifting inserts 30

341 General 30 342 Lifting position tolerances 30

35 Surface finishes 31

351 Types of finishes 31 352 Production 31 353 Tiled finishes 31

36 Prefabricated metal frames 31

37 Pre-concreting check 31

38 Concrete placing 32

39 Demoulding and lifting 32

310 Curing 32

3101 Normal curing 32 3102 Steam curing 33

311 Handling 33

312 Post-concreting check 33

3121 General 33 3122 Surface finish 33

313 Lifting equipment and accessories 34

314 Factory and site storage 34

315 Transportation 35

3151 Delivery 35 3152 Loading and storage on transporters 35

316 Erection 35

3161 Erection preparation 35 3162 Erection safety 35 3163 Erection sequence 35 3164 Missing or damaged lifting inserts 35 3165 Rigging 36 3166 Temporary bracing and supporting structures 36 3167 Levelling shims 36 3168 Propping 36 3169 Cleansing to semi-precast slab 37

317 Tolerances 37

3171 Production tolerance for precast concrete components 37 3172 Erection tolerance for precast concrete components 38 3173 Volumetric precast concrete components 39

4 Quality Control 41

41 Factory 41

411 General 41 412 Testing standards 41

42 Site 42

43 Special testing 42

431 Watertightness testing of external precast faccedilade panels 42 432 Load testing 43 433 Tiled finishes 43

Appendix A Connection Details

Appendix B Precast Concrete Faccedilade Typical Details

Appendix C Lifting Devices Typical Details

LIST OF TABLES

Table 21 ndash Recommended equivalent load factors to account for demoulding 7

Table 22 ndash Recommended equivalent load factors to account for dynamic forces arising during handling transportation and erection 7

Table 23 ndash Limits of chloride content of concrete 8

Table 24 ndash Recommended factors of safety for lifting inserts and bracing 9

Table 25 ndash Allowances for effects of spalling at supports 16

Table 26 ndash Allowances for effects of spalling at supported members 17

Table 27 ndash Values of tan f for concrete connections 20

Table 28 ndash Design ultimate horizontal shear stresses at interface 27

Table 31 ndash Recommended tolerances for lifting devices 30

Table 32 ndash Recommended minimum concrete strengths for lifting and handling 32

123 4 56 78

LIST OF FIGURES

Figure 2 ndash Types of tie in structural frame 11

Figure 2 ndash Continuity of ties bars in precast member lapped with bar in insitu concrete 13

Figure 2 ndash Continuity of ties anchorage by enclosing links 14

Figure 2 ndash Continuity of ties bars lapped within insitu concrete 14

Figure 2 ndash Schematic arrangement of allowance for bearing 16

Figure 2 ndash Back-up materials and bond breakers in movement joints 21

Figure 2 ndash Typical examples of gaskets in joints 23

Figure 2 ndash Gasket junctions Continuous grid or ladder gasket 23

1 GENERAL

11 SCOPE This Code of Practice deals with the design construction and quality control of structural and nonshystructural precast concrete elements The design method used in this code is the Limit State Design as given in the Code of Practice for Structural Use of Concrete Other alternative design approaches may also be used provided sufficient justifying calculations are submitted For bridges and associated structures reference should also be made to the Structures Design Manual for Highways and Railways issued by the Highways Department All design should be carried out under the supervision of a registered structural engineer or authorized person with the execution of the works carried out under proper supervision The requirements outlined in this code apply to both structural and non-structural members

12 DEFINITIONS For the purpose of this Code of Practice the following definitions apply

Back-up material Material inserted in a joint that controls the depth and back profile of the applied sealant

Bearing length The length of support supported member or intermediate bedding material (whichever is the least) measured along the line of support (see Figure 25)

Bearing width The overlap of support and supported member measured at right angles to the line of support (see Figure 25)

Bedded bearing A bearing with contact surfaces having an intermediate bedding of cementitious material

Bond breaker Film or thin strip of material applied to prevent sealant adhesion to the back of a joint

Dry bearing A bearing with no intermediate bedding material

Elastic sealant Sealant which exhibits predominantly elastic behaviour ie stresses induced in the sealant as a result of joint movement are almost proportional to the strain

Elastoplastic sealant Sealant which has predominantly elastic properties but exhibits some plastic properties when deformed over long periods

Equivalent monolithic system A precast concrete structural system should have strength and ductility capacity equivalent to that provided by a comparable monolithic reinforced concrete structure

Gasket Flexible generally elastic preformed material that forms a seal when compressed

Isolated member A supported member for which in the event of failure no secondary means of load transfer is available

Joint filler Compressible non-adhesive material used to fill movement joints during their construction

Net bearing width The bearing width after allowance for ineffective bearing and constructional inaccuracies (see Figure 25)

Non-isolated member A supported member which in the event of loss of a support would be capable of transferring its load to adjacent members

Plastic sealant Sealant which retains predominantly plastic properties ie the stresses induced in the sealant as a result of joint movement are rapidly relieved

Plastoelastic sealant Sealant which has predominantly plastic properties with some elastic recovery when deformed for short periods

Seal Notionally impenetrable physical barrier in contact with the components forming the joint

Sealant Material applied in an unformed state to a joint which seals it by adhering to appropriate surfaces within the joint

Sealing strip Preformed material which may have adhesive properties that forms a seal when compressed between adjacent joint surfaces

Simple bearing A supported member bearing directly on a support discounting the effect of projecting steel or added concrete

13 SYMBOLS For the purposes of this Code of Practice the following symbols apply

Gk characteristic dead load

Qk characteristic imposed load

fcu characteristic strength of concrete

fy characteristic strength of reinforcement

Other symbols are defined in the text where they occur

2 DESIGN

21 SCOPE 211 General

The considerations for design and detailing of structural and non-structural precast elements including joints and connections for buildings and building works are given in this section

212 Standards and codes of practice Precast concrete elements should be designed and constructed in compliance with the Building (Construction) Regulations and other relevant codes of practice

The design method specified in this code of practice for the design of precast concrete elements is the Limit State Design method Alternative design approaches may be used provided that sufficient justifications are given Unless otherwise specified the design considerations and detailing requirements recommended in the Code of Practice for Structural Use of Concrete should be followed

22 PLANNING 221 Standardisation

Buildings utilising precast concrete construction should be planned wherever possible to utilize standardised precast concrete elements

Most buildings will be unique and site specific At the conceptual design stage a basic layout plan should be developed which achieves a balance between architecturalaesthetic requirements and a high degree of standardisation Therefore close collaboration amongst different design parties is essential during conceptual design to achieve the optimum standardisation

222 Buildability Overall planning and detailed design should aim to achieve functionality with ease of construction

During conceptual design consideration should be given to the following

ease means of transportation and any restrictions on vehicle size access to and around the site ease of erection any overhead obstructions or power supplies size and capacity of crane available to undertake erection propping andor bracing requirements joint widths between adjacent precast elements should be sufficient to allow safe

alignment during erection and to accommodate building movement and construction tolerances jointing method structural action and cost of construction

In addition attention should be given to any special considerations affecting large sized panels particularly with regards to fabrication de-moulding and transportation

223 Voids and buried conduits Where practical all voids and service openings should be preformed Cast inburied conduits should be placed within the reinforcement layers of the pre-cast unit

224 Layout plan Structural layout plans should be a complete and comprehensive set of drawings showing plans sections elevations and connection details of the different types of precast components used

225 Compatibility Whenever there are divided responsibilities for design and details in precast construction detailed checks to ensure compatibility should be made by a designated party

226 Demolition Consideration should be given at planning stage to future demolition of the structure and any special requirements that are needed particularly with regards to prestressed structures

23 STABILITY 231 General

The overall stability of the complete structure must be checked

The temporary stability of the structure as well as that of the individual components during all stages of construction should be considered

A structure comprising precast elements must possess adequate stability to resist wind load and other lateral loads Cross walls or sway frames should be so arranged as far as practicable so as to provide lateral stability

Many precast concrete structures are designed as pin jointed rather than with moment continuity as is the case with insitu concrete frames The absence of the rigid frame means that in the case of buildings transverse stability is generally provided by shear walls with floors transferring load by acting as horizontal plates It is therefore essential to provide adequate ties between elements

If wind load does not govern stability should be checked for a minimum notional horizontal force acting at each floor level equals to 15 of the characteristic dead load between mid-heights of the storey under and above or the roof surface as appropriate

Consideration should be given to lateral stability during all stages of construction and erection where the behaviour of the precast elements may differ from the permanent condition Adequate propping and bracing should be provided at all stages of construction to ensure stability is maintained at all times A viable scheme showing how temporary stability is provided at each construction stage should be produced The temporary works scheme should provide sufficient details including propping layouts for all stages of construction including the sequencing and timing of the dismantling of temporary works

Particular attention should be given to stability and bracing requirements on high risk structures such as long span beams and high rise buildings

232 Displacement 2321 General

Structural members should possess adequate stiffness to prevent such deflection or deformation as might impair the strength or efficiency of the structure or produce cracks in finishes or in partitions The structure as a whole should possess adequate stiffness such that the maximum lateral deflection due solely to wind forces does not exceed 1500 of the building height In determining the total lateral deflection an allowance should be included for the cumulative effects of deformation of connections (see clause 2322)

2322 Connection deformation In determining the overall lateral displacement allowance must be made for slippage and deformation of connections in all structural elements The cumulative value of deformation of connections at each level should be added to the deflection calculated from the structural analysis and the total value should comply with the limitation specified in clause 2321

233 Disproportionate collapse Precast building structures should also be checked for disproportionate collapse as a result of progressive failure or the like

24 DURABILITY 241 General

It is important to consider the required design life and durability of precast elements For this purpose the following factors are to be considered

shape and size of the precast unit concrete constituents concrete cover the environmental exposure protection against fire protection and maintenance production transportation storage and installation and design of joint details

In addition to the requirements given above the recommendations specified in the Code of Practice for Structural Use of Concrete and the Building (Construction) Regulations should be followed

242 Shape of precast unit The precast unit should be designed and detailed to have good drainage such that no standing pools or excessive trapped moisture would occur

Sharp corners or sudden changes in section cause stress concentrations that may lead to cracking or spalling of concrete and therefore should be avoided Where sharp corners or sudden changes in section cannot be avoided because of practical reasons stress concentrations should be checked and strengthening be provided as necessary

Buckling and instability should be avoided during lifting and erection of long slender precast units Lifting inserts should be located to ensure that compression flange buckling would not occur particularly during manoeuvring of precast units

243 Concrete cover Cover for precast elements should be no less than those specified for reinforced concrete structures

In respect of concrete cover requirements for protection against fire the Code of Practice for Fire Safety in Buildings should be followed whereas for protection against corrosion the requirements under the Building (Construction) Regulations should be adopted

For bridges and associated structures reference should also be made to the requirements specified in the Highways Departmentrsquos Structures Design Manual for Highways and Railways and the most onerous requirements should be used

The cover to all brackets and fixings etc should comply with the minimum cover requirements specified for reinforcement

The fire resistance of joints fillers etc should comply with the fire resistance requirements of the precast members

244 Protection and maintenance of joints and connections 2441 General

To achieve durability connections should be properly filled with suitable material to prevent corrosion cracking or spalling of concrete

2442 Protection of steel Steel except those for temporary use such as lifting anchor used at connections should be protected with an adequate thickness of concrete mortar or grout The effectiveness of bonding of concrete or grout to steel surfaces must be considered

2443 Protection of fixings If sufficient concrete cover cannot be provided to protect the fixings at connections corrosion-resisting materials such as galvanised mild steel or stainless steel shall be used

2444 Maintenance accessibility The importance of the connection and its readiness for inspection usually dictate the type of protection required Connections that are not accessible for inspection should be properly protected from corrosion

245 Movement To avoid concrete spalling and cracking allowance should be made for movement (see clause 277)

246 Thermal gradient Reinforcing steel preventing cracking of concrete should be provided in both faces of panels that are subjected to substantial thermal gradients

247 Other effects Indirect effects resulted from loading changes temperature differentials creep shrinkage etc can affect the behaviour of structures

Apart from compliance with general requirements for durability cracking and deformation strength and stability the following may have to be considered

limiting the cracking and deformation arising from early-thermal movement creep shrinkage etc or minimising restraints on structural components by providing bearings or movement joints

or if restraints are inevitable the design should take into consideration any significant effects that may arise

25 LOADINGS 251 General

The appropriate loading requirements as specified in the Building (Construction) Regulations and the Code of Practice for Dead and Imposed Loads should be complied with

Design considerations should also be given to

construction loads A minimum load of 15 kNmsup2 should be used However due consideration should be given to any special requirements eg for plant loads or storage loads and the load increased accordingly notional horizontal load The lateral load should be taken as not less than 15 of the

characteristic dead load (refer also to clause 231) and accidental loads such as earth movement impact of construction vehicles

252 Demoulding forces An allowance should be made for the forces on the element due to suction or adhesion between the precast element and the mould when precast elements are lifted from a casting bed These are accounted for by applying an equivalent load factor to the member self weight and treating it as an equivalent static force to evaluate the stresses in the precast element against the commensurate early strength attained Table 21 gives recommended values of equivalent load factor for demoulding forces for different product types and finishes

Table 21 ndash Recommended equivalent load factors to account for demoulding

Product type Finish

Exposed aggregate with retarder

Smooth mould (form oil only)

Flat with removable side forms No formed rebates or reveals 12 13

Flat with removable side forms Formed rebates or reveals 13 14

Fluted with proper draft 14 16

Sculptured 15 17 Notes 1 These factors are to be applied to the flexural design of precast elements only For lifting inserts refer to Table 24 2 The above values are recommended values only Guidance should also be sought from the precast manufacturer to

verify their suitability 3 The associated imposed loads or wind loads if any are to be assessed and considered under the appropriate load

combination 253 Handling and transportation

An allowance should be made for dynamic loads and impact forces arising during handling transportation and erection Similar to demoulding force consideration Table 22 gives recommended values for equivalent load factor to be applied to the self weight of members to allow for these forces

Table 22 ndash Recommended equivalent load factors to account for dynamic forces arising during handling transportation and erection

Stage Load factor

Yard handling 12

Transportation 15

Erection 12 Notes 1 These factors are to be applied to the flexural design of precast elements only For lifting inserts refer to Table 24 2 The above values are recommended values only Under certain conditions higher factors may apply ie certain

unfavourable road conditions 3 The associated imposed loads or wind loads if any are to be assessed and considered with the appropriate load

combination

26 MATERIALS 261 General

For the requirements on the use of materials the Building (Construction) Regulations should be followed The material properties used for design should be obtained from the Code of Practice for Structural Use of Concrete

262 Alkali-aggregate reaction 2621 Alkali-silica reaction

Aggregates containing silica minerals are susceptible to attack by alkalis (Na2O and K2O) from the cement or other sources Alkali-silica reaction causes cracking and reduces the strength of concrete

Effective means of reducing the risk of alkali aggregate reaction include

control on the amount of cement used in the concrete mix use of a low alkali cement use of an appropriate cement replacement such as pulverised fuel ash (pfa) and the reactive alkali content of concrete expressed as the equivalent sodium oxide per

cubic metre should not exceed 30 kg

The concrete supplier should submit to the authorized person or registered structural engineer a mix design and Hong Kong Laboratory Accreditation Scheme (HOKLAS) endorsed test certificates giving calculations and test results demonstrating that the mix complies with the above limitation on reactive alkali content

2622 Alkali-carbonate reaction Some carbonate aggregates may be susceptible to alkali-carbonate reaction which is similar to alkali-silica reaction in its effects If carbonate aggregates are to be used specialist advice should be obtained

263 Chlorides in concrete Reinforcing steel is susceptible to corrosion with the presence of chloride in concrete

The total chloride content of the concrete mix arising from the aggregate admixtures and any other source should not exceed the limits given in Table 23

The total chloride content should be calculated from the mix proportions and the measured chloride contents of each mix constituent

Table 23 ndash Limits of chloride content of concrete

Type or use of concrete Maximum total chloride content expressed as a percentage of chloride ion by mass of cement

Prestressed concrete Steam-cured concrete 010

Concrete made with sulphate resistant cement 020

Concrete with embedded metal and made with Ordinary or Rapid Hardening Portland cement

inclusive of pulverised fuel ash or ground granulated blast furnace slag when used

27 DESIGN CONSIDERATIONS 271 General

The recommended methods for design and detailing of reinforced concrete and prestressed concrete given in the Code of Practice for Structural Use of Concrete also apply to precast concrete elements In addition the following should also be considered

handling stresses early lifting of precast element temporary stages erection sequence lifting inserts bracing design design for movement design of ties and design of bearings

272 Handling stresses Precast units should not be inflicted with any permanent damage arising from their handling storage transportation and erection Consideration should be given during design to

loads on erected elements at construction stage (refer to clause 251) and demoulding storage transportation and erection of precast units on site (refer to clauses

252 and 253)

273 Early lifting of precast element Where precast elements are lifted and handled prior to gaining full strength the elements together with any lifting inserts should be designed accordingly Recommended minimum concrete strengths for lifting and handling of precast elements are given in Table 32 Precast elements should be designed using these lower strengths to span between lifting points without excessive cracking or deflection

For prestressed concrete consideration should also be given to stresses resulting from transfer of prestressing forces

274 Temporary stageserection sequence The critical loading for precast elements is often not the permanent condition but can occur during the construction phase and hence the temporary condition may govern the design of elements Consideration should be given to the loading imposed on precast elements during each phase of construction Examples of such cases are as follows

precast sections of composite elements which are required to support self weight plus construction load prior to casting of an insitu topping lower precast floor slabs or precast stair flights which support propping to upper levels

during installation and bearing or halving joints which support higher temporary construction loads because of

back propping to upper levels The design should also take into consideration that the structural action and framing might be different during the temporary stages resulting in higher stresses in individual members

275 Lifting inserts 2751 General

When determining the number and location of lifting inserts the following should be considered

lifting insert capacity (safe working load) total weight of the element strength of concrete at age of lifting (see clause 273) shape of the unit location of the inserts so that the failure of any one insert does not cause failure of the

entire lifting system thereby ensuring the element can still be safely supported position of any cut-outs andor openings and rigging arrangement

All lifting inserts should be purposely designed proprietary products Reinforcing bars may only be used as lifting inserts if specifically designed and installed for this purpose

Table 24 gives recommended factors of safety at ultimate limit state for designing of lifting inserts

Typically lifting inserts should be designed with a factor of safety of 4 Where they are to be used for multiple lifts such as manhole covers a factor of safety of 5 should be used These factors are at ultimate limit state

Lifting inserts should be tested or evidence of testing of inserts to the ultimate load should be provided

Table 24 ndash Recommended factors of safety for lifting inserts and bracing

Item Recommended factor of safety

Bracing members 2

Bracing connections 3

Bracing inserts cast into precast members 3

Lifting inserts normal circumstances 4

Lifting inserts multiple usage 5

2752 Anchorage All lifting inserts require adequate embedment or anchorage to function effectively Factors affecting anchorage include the following

proximity to element edges openings rebates or arises proximity to other concurrently loaded lifting devices concrete strength at lifting concrete thickness depth of embedment presence of cracking proximity of reinforcement or pre-stressing tendons and tensile stresses in the concrete around the insert

Guidance should be sought from the manufacturer when determining the safe working load of the inserts taking into consideration the above factors

2753 Additional reinforcement Where additional reinforcement is required in the vicinity of the insert to generate the full load capacity of the insert it should be detailed in accordance with the Code of Practice for Structural Use of Concrete and the manufacturerrsquos recommendations

276 Bracing design Bracing should be designed for both construction and wind loading The construction load should be a minimum value of 15 kNmsup2 but should be increased if considered appropriate

Wind loads should be calculated in accordance with the Code of Practice on Wind Effects in Hong Kong

Recommended load factors for design of bracing and connections are given in Table 24

277 Design for movement Provision for movements is of great importance in precast construction The type number and spacing of joints should be determined at an early stage in the design and will be dependent upon the cumulative movement expected In determining the width of the joint allowance should also be made for production and erection tolerances (refer to clause 317) Causes of movements in structures include the following

creep deformations early thermal shrinkage long term shrinkage differential settlement thermal movement due to seasonal changes of temperature and thermal movement due to temperature difference between internal and external

environments When determining the range of movement for a particular joint it should be borne in mind that not all movements are coexistent and the timescale over which different types of movement will occur should be taken into consideration Also due regard should be given to ambient temperature and age of precast elements and stage of construction at the time of formation of the joint

The designer should also take into account the effects of eccentric moments caused by eccentricities from production and erection tolerances and cumulative moments at joints

When precast units are incorporated into a structural system the forces and deformations occurring in and adjacent to connections should be included in the design Tolerances for precast units and interfacing members should be specified Design of precast units and connections joints should include the effects of these tolerances

278 Design of ties 2781 General

To allow for damage or prevent progressive failure due to accidental loads which may result in the failure of a load bearing element horizontal and vertical ties (or their equivalent) must be provided Such ties provided should be continuous and may be within the insitu concrete topping or precast units or partly within both the precast and insitu concrete The various types of ties are to be designed to resist the minimum tensile forces as defined in clauses 2784 to 2788

In the design of the ties forces other than those given in clauses 2784 to 2788 may be ignored

2782 Provision of ties Tie reinforcement should be designed to resist forces mentioned in clauses 2784 to 2788 whereas reinforcement provided for other purposes in columns walls beams and floors may be regarded as providing part of or the whole of these ties A material partial safety factor of 1 can be used when determining the area of reinforcement required

2783 Types of ties The types of ties to be provided for stability and interaction between precast units are as follows

internal ties peripheral ties horizontal ties to column and walls corner column ties and vertical ties to columns and walls

Figure 21 shows a typical example of ties in building structures

Figure 21 ndash Types of tie in structural frame

Internal ties (a) Distribution

At each floor and roof internal ties should be provided in two perpendicular directions They should be continuous and except for horizontal ties to walls or columns they should be anchored to the peripheral ties at each end They may be distributed evenly in the slabs or grouped in walls or at other suitable locations Their spacing should generally be not greater than 15 l (l equals the span length in the directions of the ties (in m) between the centres c cof the columns frames or walls whichever greater) In walls they should be within 05m of the top and bottom of floor slabs

(b) Strength Ties should be designed to resist in each direction a tensile force T (in kNm) equal to the greater of

G Q lk k c or T F 75 5

T = 10F

Gk is the average characteristic dead floor load (in kNmsup2)

Qk is the average characteristic imposed floor load (in kNmsup2)

l is as defined in 2784 (a) c

F is defined as the lesser of (20 + 4n) or 60 where n is the number of storeys

For structures with single direction cross or spine walls the length l for calculating the tie c force in the direction of the wall should be the lesser of the actual length of the wall or the collapsed length in case of an accident The collapsed length should be the distance between adjacent lateral supports or between a lateral support and a free edge of the wall under consideration

Peripheral ties Peripheral ties should be provided at each floor and roof level for resisting a tension of 10 F (in kN per metre width) The peripheral ties should be placed within 12 m of the edge of the building or within the peripheral wall

Horizontal ties to columns and walls Every metre length of external bearing wall unless the peripheral tie is located within that wall should be anchored or tied horizontally into the structure at each floor and roof level Every such tie should be able to resist a tension (in kN) equals to the greater of

h the lesser of 20 F or F where h (in m) is the clear storey height or

25 3 of the total design vertical load of the column or wall at that level

Where the peripheral tie is placed within the wall or column only horizontal ties or anchors as required in clause 2784 need to be provided

Corner column ties Corner columns should be tied into the structure at each floor level in orthogonal directions as far as practicable The ties should each be able to resist a force as calculated in accordance with clause 2786

Vertical ties to columns and walls Each bearing wall or column should be tied continuously at all levels The tie should be able to resist a tensile force equal to the maximum design dead and imposed load at the column or wall from any one storey

2789 Tie anchorage A tie crossing another tie at right angles may be considered anchored if the bars extend

12 times the bar diameter or an equivalent anchorage beyond the other tie or an effective anchorage length calculated from the tension force beyond the centre-line

of the other tie At abrupt changes in construction or at re-entrant corners it is necessary to ensure that the ties are sufficiently anchored or to be made effective by other means

27810 Continuity of ties A continuous tie must satisfy clause 2813 The minimum thickness of insitu concrete section where tie bars are provided should be at least the total dimension of the bar diameter (or two diameters at laps) and twice the maximum aggregate size plus 10 mm

To provide continuity the tie should also satisfy one of the following

a bar in a precast concrete unit lapped with a bar encased in insitu concrete bounded on two opposite sides by rough faces of the same precast unit (see Figure 22) a bar in a precast concrete unit lapped with a bar encased in the topping of insitu

concrete tied to the precast unit by links or stirrups The tensile resistance of such links and stirrups should not be less than the designed tension in the tie (see Figure 23) bars lapped within insitu topping concrete with projecting links or stirrups from the

supporting precast units such as beams or slabs (see Figure 24) or bars extended from the precast units connected by a method as given in clause 2813

Figure 22 ndash Continuity of ties bars in precast member lapped with bar in insitu concrete

Figure 23 ndash Continuity of ties anchorage by enclosing links

Figure 24 ndash Continuity of ties bars lapped within insitu concrete

27811 Anchorage in structures All precast floor and precast roof units should be effectively anchored if these units are not utilised to provide the ties in accordance with clauses 2781 to 2788 The anchorage should be capable of supporting the dead weight of the precast unit to that part of the structure which contains the ties

27812 Eccentricity Ties connecting precast floor or roof units should be so designed and placed as to minimise eccentricity

27813 Anchorage at supports In case reinforcing bars are used to provide the structural integrity of slab ends supported on corbels or nibs great care must be taken to ensure it is adequately lapped and anchored (see clauses 2789 and 27810) Allowance should also be made for constructional inaccuracies (see clause 2799)

279 Design of bearings 2791 General

The integrity of a bearing is preserved by three essential measures

an overlap of reinforcement in reinforced bearings a restraint preventing loss of bearing due to movement and an allowance for the cumulative effects resulting from production and erection tolerances

(see clause 317)

2792 Net bearing width of non-isolated members The net bearing width for a member should be taken as

ultimate support reaction Net bearing width = effective bearing length x ultimate bearing stress

or 40 mm whichever is greater

(See clause 2793 for determination of the effective bearing length and clause 2794 for the design ultimate bearing stress)

The net bearing width should be increased to cater for any free movement permitted or rotation of the bearing about the support

2793 Effective bearing length The effective bearing length of a member is the lesser of

bearing length one-half of bearing length plus 100 mm or 600 mm

2794 Design ultimate bearing stress The design ultimate bearing stress is based on the weaker of the two bearing surfaces and is calculated as follows

04fcu for dry bearing on the concrete 06fcu for bedded bearing on concrete or 08fcu for contact face of a steel bearing plate cast into a member or support with each

dimension not exceeding 40 of the corresponding concrete dimension An intermediate value of bearing stress between dry and bedded bearings may be used for flexible bedding

2795 Net bearing width of isolated members The net bearing width for isolated members should be that of non-isolated members plus 20 mm

2796 Detailing for simple bearing Over and above the net bearing width calculated in accordance with 2792 allowances for spalling and constructional inaccuracies should be made in the nominal width selected (see Figure 25) The effects of accidental displacement of a supported member during erection should also be considered The minimum anchorage lengths of reinforcement required by the Code of Practice for Structural Use of Concrete should be provided

Figure 25 ndash Schematic arrangement of allowance for bearing

2797 Allowances for spalling at supports Recommendations for the allowances of ineffective portion of bearing area are given in Tables 25 and 26 When determining the outer edge of a support or the end of a supported member chamfers occurring within the areas subjected to spalling may be discounted

Table 25 ndash Allowances for effects of spalling at supports

Material of support Distance assumed ineffective (mm) (measured from outer edge of support)

Steel 0

Concrete grade 30 or above plain or reinforced (in general)

Concrete less than grade 30 plain or reinforced (in general)

Reinforced concrete with outer edge less than 300mm deep where vertical loop is not greater than 12mm diameter

Nominal end cover to reinforcement on outer face of support

Reinforced concrete with outer edge less than 300mm deep where vertical loop is 16mm diameter or above

Nominal cover plus inner radius of bend of bars

When particular constituent materials are used in concrete adjustment to the distances assumed should be made

Table 26 ndash Allowances for effects of spalling at supported members

Reinforcement at bearing ofsupported member

Distance assumed ineffective (mm)(measured from end of supported member)

Straight bar horizontal loops or vertical loops of 12 mm diameter or less

The greater of 10 mm or nominal end cover

Tendons or straight bars exposed at end of member

Vertical loops of 16 mm diameter or above Nominal end cover plus inner radius of bend of bars

2798 Steel shims Steel shims should not be used at areas that are susceptible to spalling It is essential that steel shims should be removed after grouting When joint details are prepared it should be demonstrated that all shims can be easily removed Where steel shims cannot be removed the effect of load transfer via the shims should be designed for

2799 Allowance for construction inaccuracies The cumulative effect of construction inaccuracies and manufacturing tolerances should be allowed for Recommendations for tolerances are given in clause 317 for production and erection respectively

The provision of clearances is recognised by the designer and the fabricator of the need for interface tolerances Clearance should provide a buffer area where combined erection and production variations can be absorbed and the actual clearance provided should reflect all the specified tolerances The minimum combined total tolerance allowed should be at least equal to the square root of the sum of the individual tolerances squared

27910 Bearings transmitting compressive forces Where a bearing is required to transmit vertical load from a wall which extends over the end of a supported member a bedded bearing should be used

27911 Other forces at bearings (a) Horizontal forces at bearing

The horizontal forces at bearings may be induced by creep shrinkage temperature effects misalignment lack of plumb or other causes When these forces are significant the structural capacity of the supporting member may be impaired Allowances should be made by the provision of

sliding bearings which allow longitudinal and lateral movement additional lateral reinforcement at the top of the supporting member or continuity reinforcement which ties the ends of the supported members

together (b) Rotation at bearing

Suitable bearings should be used to accommodate the rotations at end supports in particular for flexural members Allowances should be made for any consequential increases in bending moments or bearing stresses due to rotations

27912 Concrete corbel The design and reinforcement detailing of corbels should be in accordance with the Code of Practice for Structural Use of Concrete

28 JOINTS AND CONNECTIONS 281 Structural connections 2811 General

The overall stability of a building and the temporary stability of individual members during construction should be checked The recommendations of clause 23 should be followed Handling and construction stresses should be considered Creep effects for prestressed members should also be considered If connection failure could result in a catastrophic failure of the structure these connections should be avoided and the registered structural engineer should use a detail appropriate to the circumstance

Requirements for anchorage and continuity of ties at connections are given in clauses 2789 and 27810 Account should be taken of the effects on connections of movements and whether or not these need to be specifically catered for

The recommendations for design of joints are given in clause 282

A free flowing self-compacting and non-shrink grout should be used at the interface with the precast elements to minimise the risk of cracking and to ensure good compaction at the connection

For some precast elements such as semi-precast balconies or lost forms the preparation and specification of the construction joints should be carefully monitored and specified to ensure that the design is adequate and the intent and details are reflected in the construction details

The fire resistance and durability requirements for connection should be at least similar to the members being connected

2812 Design The design of connections should follow those design methods and considerations for reinforced concrete prestressed concrete and structural steel Otherwise the connection design should be based on tests

2813 Detailing of reinforcement (a) General

The design of connections should take into account those assumptions made in the analysis of the overall structure as well as those elements at critical sections

(b) Lapping of bars Where bars passing through the connection are lapped to provide continuity of reinforcement the recommendations of the Code of Practice for Structural Use of Concrete and clause 27810 of this code apply

(c) Reinforcement grouted into aperture An adequate capacity should be provided for grouted reinforcing bars to prevent pullout

(d) Reinforcement loops Where dowel bars pass through overlapping loops of reinforcement which project from each supported member to provide continuity over a support the bearing stress of the loops should be in accordance with the Code of Practice for Structural Use of Concrete

(e) Couplers Reinforcement may be connected by couplers The concrete cover to the couplers should not be less than that specified for reinforcement

A locking device should be used for threaded coupler connections where there is a risk of the threaded connection working loose eg during vibration of insitu concrete Reference should be made to the relevant Standards and the manufacturersrsquo technical specifications for guidance and acceptance criteria for the usage and testing of couplers

(f) Welding of bars When bars are connected by welding the connection should be designed to accommodate the forces applied Reference should be made to the relevant Standards and the manufacturersrsquo technical specifications for guidance and acceptance criteria for the work and testing of welding bars

(g) Sleeving Either of the following types of sleeve may be used for jointing provided the strength and deformation of the connection have been determined by test

grouted resin-filled or swaged sleeve capable of transmitting both tensile and compressive forces or

sleeves that mechanically align the square-sawn ends of two bars to allow the transmission of compressive forces only

The maximum bar size used for the sleeved connection should be carefully considered taking into account the necessary force transmission and anti-bursting considerations as well as practical considerations to avoid congestion with other reinforcement bars in the precast elements The design manufacture and method of assembly of the sleeved joint should ensure the accurate alignment of the ends of the two bars into the sleeve The sleeve should be provided with concrete cover not less than that specified for normal reinforcing bars

2814 Connections in compression The connection should be designed to resist the forces and moments derived from the analysis of the structure In normal circumstances the area of concrete to be utilised for calculating the strength of the connection in a wall or column should be the greater of

75 of the area of contact between the wall or column and connection or the area of the insitu concrete excluding the part of any intruding slab or beam units

However those parts of the floor slab or beam units that are solid over the bearing may be included in calculating the strength and such units should be properly bedded on concrete or mortar of adequate quality This area should not be taken as greater than 90 of the wall or column area

2815 Connections in shear A shear connection may be assumed effective if the connection is grouted with a suitable concrete or mortar mix of adequate strength and one of the following conditions is satisfied

(a) Units transmitting in-plane shear The units should be restrained from moving apart Provided the design ultimate shear stress in the connection does not exceed 023 Nmmsup2 reinforcement need not be provided in or across the connection and the sides of the units forming the connection may have a normal finish Smooth moulded finishes should be roughened

(b) Joints under compression Shear stress less than 045 Nmmsup2 Provided the design ultimate shear stress does not exceed 045 Nmmsup2 and the sides or ends of the panels or units forming the connection have a rough as-cast finish reinforcement will not be required

(c) Shear stress less than 13 Nmmsup2 Where the shear stress due to ultimate loads calculated on the minimum root area of a castellated connection is less than 13 Nmmsup2 separation of the units normal to the connection should be prevented under all loading conditions by either steel ties across the ends of the connection or by the compressive force normal to the connection The projecting keys of a castellated connection are usually tapered to ease the removal of formwork However the taper should not be excessive in order to limit any movements in the connection

(d) Shear reinforcement provided The entire shear force V due to design ultimate loads should not exceed V = 06 Fb tan f

where Fb is 087fyAs or the anchorage value of the reinforcement whichever is the lesser As is the minimum area of reinforcement f is the angle of internal friction between the faces of the connection Note tan f can vary between 07 and 17 and is best determined by tests However for concrete-to-concrete connections the values used may be taken from Table 27

Table 27 ndash Values of tan f for concrete connections Type of surface tan f

Smooth interface as in untreated concrete 07 Roughened or castellated connection without continuous insitu strips across the ends of connection 14

Roughened or castellated connection with continuous insitu strips across the ends of connection 17

2816 Examples of connections Examples of typical connections are shown in Appendix A These connections are for illustrative purposes only In all instances the design should demonstrate that the connections are able to resist the applied structural actions Where appropriate the suitability of the connection to act as a pinned or moment connection is highlighted

282 Joints 2821 Scope

This section deals with the detailing of joints between external precast panels ensuring that the joints are watertight against the wind and rain Guidance is given on the design of joints and examples of typical joints are illustrated

The performance of a specific joint is critically influenced by the exposure conditions the joint movements and the properties of the jointing materials used The typical details given in this code are provided for general guidance For optimum performance and maximum life specific advice should always be sought from the manufacturers of the materials used

2822 Sealants for joints (a) General

In choosing the appropriate type of sealant for the joints consideration should be made in respect of the movements between the components to be joined the bond that is achievable between the components and the sealant and the nature of the sealing material itself

Sealants are classified as elastic elastoplastic plastoelastic or plastic according to their response to movement

(b) Joint width Joint widths should be sized to accommodate construction tolerances and the accommodation of movements without overstressing the jointing material Irrespective of movement a joint width of 5 mm is the minimum practicable for sealant application

(c) Joint preparation Satisfactory performance is critically dependent on the satisfactory adhesion of the sealant to the joint surfaces Primers may be recommended by the manufacturer for some materials Formwork oils curing compounds silicone waterproofing admixtures and surface coating materials may reduce bond and require special precautions

Water jetting sand blasting wire brushing or the use of retarder may be required to prepare the concrete joint surfaces in certain instances

Consideration should be given to the use of chamfers to reduce edge damage

2823 Back up material and bond breaker To ensure good adhesion a firm backing should be provided for the application of sealants The required shape and proportions of the sealant are achieved by the correct installation of the back up material

Sealants in movement joints should not adhere to the backing material to avoid any unnecessary restraint

To ensure that the sealant and back up materials bond breakers and joints fillers are compatible and appropriate for the proposed end use advice from the manufacturer should be obtained as necessary

The sealant backing may be provided by a closed cell foam back up material alone (see figure 26a) a thin self-adhesive bond breaker tape (see figure 26b) or a joint filler separated from the sealant by a thin self-adhesive bond breaking tape (see figure 26c)

Figure26 ndash Back-up materials and bond breakers in movement joints

(a) Minimum joint gap widths The minimum joint gap width should be derived to accommodate the construction and manufacturing tolerances the range of movements anticipated the required dimensions of the sealant to accommodate those movements and the desired appearance

A minimum joint width of 12 mm between panels is a common practice However for structural movement joints a joint width of 50 mm or more may be required Joints of such width require special sealant properties to avoid slump

For elastic sealants the minimum thickness should be 5 mm the ratio of width to thickness should never exceed 11 and for optimum performance 21

(b) Sealant application High moisture content may be detrimental to the adhesion of the sealant Sealing should not be undertaken if there is free water present on the surface of the concrete

(c) Types of movement (i) General

The magnitude of the movement and also the mode frequency and rate of movement affect the performance of a sealed joint

(ii) Choice of sealant There are many factors affecting the choice of sealant suitable for the different types of movement However as a general rule joints which have to accommodate frequent and rapid movement need an elastic sealant while joints in massive components with high thermal inertia resulting in much slower movement may be satisfactorily sealed with an elastoplastic plastoelastic or a plastic sealant

(iii) Types and causes of failure of sealants The different ways in which sealants can fail as a consequence of different factors including climatic conditions environmental factors substrate incompatibility abrasion and traffic loading need to be considered when selecting a sealant

2824 Gaskets (a) General

Gaskets are used to provide a barrier against wind and rain They are required to be under compression at all times for proper functioning

(b) Materials Gaskets made of natural rubber compounds have to be protected from the weather by a synthetic rubber skin For special properties such as resistance to oils synthetic rubbers and plastic materials have to be specifically formulated for the intended use Gaskets can be various profiles of solid or hollow section formed from cellular or non-cellular material or combinations of these sections or materials Variations in the mechanical properties of cellular gaskets are achieved by variations in density material hardness and cell size and whether or not cells are interconnecting

Cellular materials have a relatively shorter service life in general unless they are protected from UV degradation by an outer skin of non-cellular material

Cellular material is available in sheets with or without adhesive and backing paper and can be cut to provide simple relatively inexpensive gaskets

Open cell materials are available impregnated with waxes or bituminous compounds and may also be adhesive coated

(c) Design (i) General

The selection of components and their edge profiles the method and sequence of installation and the type of gasket are inter-related It is always advisable to consult manufacturers at an early stage in the joint design When designing gasket sealed joints the recommendations of clause 2824(c) (ii to vii) should be considered

(ii) Primary and secondary seals Gasket joints should be designed to provide primary and secondary points of gasket contact having an air space between them (see figure 27(b) and 27(c))

Figure 27 ndash Typical examples of gaskets in joints

(iii) Continuity at junctions between horizontal and vertical gaskets For gaskets to be effective continuity of seal should be provided at the junctions between the horizontal and vertical gaskets These complex junctions are best produced as factory made joints incorporated as part of a gasket grid so that site jointing is limited to simple butt joints (see figure 28)

Figure 28 ndash Gasket junctions Continuous grid or ladder gasket

Gaskets connected by butt joints should only be used where good protection and effective continuity are provided at the joint Where continuity cannot be achieved especially at junctions in vertical joints it is necessary that effective drainage weather protection and adequate gasket overlaps are provided

(iv) Movement joints When used in movement joints gaskets should be deformed sufficiently to maintain compression over the entire movement range yet not be so highly compressed as to incur significant compression set For example a cellular neoprene gasket should not be compressed in service more than 50 of its uncompressed thickness

Gasket seals in movement joints can be fully effective from the completion of the installation

(v) Installation Care is needed in handling gaskets to avoid deformation or damage Although the preparation of surfaces is not as critical as for sealants it is essential that all surfaces should be clean sound and free from gross imperfections To ease the insertion of gaskets into a joint lubricants recommended by the manufacturer may be used Where possible gaskets should not be stretched during installation However if this is unavoidable sufficient time should be given for the gaskets to recover before trimming

(vi) Force The force necessary to compress a length of gasket in a joint can be considerable particularly when the joint is assembled in the sequence componentgasket component As a result gaskets when correctly installed may exert force such force should be taken into account in the course of design

(vii) Durability The useful life of gasket materials has to be considered at the design stage In movement and other important joints gasket life may be less than the building life The conditions of use qualities of materials etc determine the actual life of the gasket It may be necessary to specify that seals may need major attention or replacement during the life of the structure

2825 Sealing strips (a) General

Preformed sealing strips are available in a range of sizes and sections There are two basic types

mastic strips and impregnated or coated cellular strips

(b) Mastic strips These are normally installed during the assembly of components They require an initial compression to ensure proper adhesion to the components forming the joint As a degree of compression is also required during in service mastic strips are unsuitable for joints which open beyond their assembled size

(c) Impregnated or coated cellular strips These may be supplied in a pre-compressed form and one face may be adhesive coated When pre-compressed they can readily be installed within the joint gaps but should be of a suitable size to be maintained under the degree of compression specified by the manufacturer throughout the range of joint movements The degree of compression may be varied according to the level of sealing performance required

To ensure uniformity of compression and stability of the seal it is important that the joint faces are parallel Seal stability is also influenced by the installed depth to width ratio of the seal which should not exceed 11 in service At installation a ratio of 21 should be achieved Sufficient joint depth must be provided to accommodate the seal with these depth to width ratios

For external applications sealing strips should have adequate exposure resistance for the proposed service conditions

2826 Joint fillers (a) General

Fillers for movement joints should be carefully selected to suit their intended use To ensure that the sealant and filler are compatible advice from the manufacturer should be sought

Expanded polystyrene is not a suitable material for a joint filler

(b) Functions

Joint fillers have the following functions

form part of the initial joint during construction provide a barrier to dirt or debris which could prevent joint

closure control the depth of sealant in the joint and support the sealant

(c) Properties

Joint fillers require the following properties

should be compressible should not be extruded from the joint should have resilience should be non staining should not contain cellulose to prevent termite investation should have resistance to damage in handling and should not present a fire hazard

2827 Overlapping of precast faccedilade The resistance to water penetration between the upper and lower panel of precast faccedilade is commonly provided by an upstand profile A minimum overlap of 75mm between the upper and lower panel is recommended

2828 Testing Precast panels often include cast in window frames and the window assemblies are commonly subjected to tests for the infiltration of air and water To test the potential joint performance consideration may be given to incorporating panel to panel joints in the window test assembly

The most effective test as it encompasses site workmanship and also can encompass a large number of joints is inspection of the completed panel joints for damp or leakage after heavy rain at site

In the absence of heavy rain specific joints can be tested by spraying them with water The hose should deliver water as a spray not a solid jet and the water should be directed horizontally not upward (see clause 431 for water-tightness testing of faccedilade panels)

2829 Maintenance The design of joints should allow for inspection repair and if necessary replacement of deteriorated jointing products during maintenance All joints should be designed in a manner that should be accessible for inspection and repair without major disruption to the building occupants However for practical reasons the temporary removal of some interior decoration might be necessary

Building maintenance manuals should be provided to include the following

an inspection schedule an expected replacement schedule for jointing products an identification of joints where lack of maintenance would lead to significant

consequential damage

guidance on how to maintain joints and means to identify products or types of jointing products used

29 COMPOSITE CONCRETE CONSTRUCTION 291 General

Where reinforced or prestressed precast concrete units are connected with insitu concrete to resist flexure provision for horizontal shear transfer at the contact surface should be made Sufficient bond at the interface of the precast element and the insitu concrete should also be provided Testing should be conducted if necessary

2911 Analysis and design The analysis and design of composite concrete structures and members should be in accordance with the Code of Practice for Structural Use of Concrete

2912 Construction methods The construction methods used should be compatible with the design of component parts as well as the composite sections Where props are used stresses and deflections should be checked to be within allowable limits

2913 Relative stiffness The relative stiffness of members should be determined from the concrete gross or transformed section If the concrete strengths of the two components of a composite member differ by more than 10 Nmmsup2 a transformed section making allowance for such difference should be used Otherwise the concrete gross section should be used

2914 Precast pre-tensioned units designed as continuous members When the designed continuity is made by reinforced concrete cast insitu over the supports the compressive stresses due to prestress in the ends of the units may be ignored over the transmission length for the tendons

2915 Differential shrinkage (a) General

Differential shrinkage may lead to increased stresses in the composite section where there is an appreciable difference between the age and quality of the concrete in the individual components and these stresses should be checked The effects are likely to be more severe when the precast component is reinforced concrete or prestressed concrete with an approximately triangular distribution of stress due to prestress The tensile stresses induced by differential shrinkage should also be considered at design stage

(b) Tensile stresses The differential shrinkage coefficient (the difference in total free strain between the two components of the composite member) needs to be established to calculate the resultant tensile stresses The various factors affecting the coefficient have to be considered and taken in to account

(c) Approximate value of differential shrinkage coefficient In the absence of exact data when designing precast T-beams with an insitu concrete flange a value of 100x10-6 may be assumed for the differential shrinkage coefficient within buildings in a normal environment

2916 Horizontal shear force due to ultimate loads The horizontal shear force due to ultimate load at the interface of the precast and insitu components is either

the total compression (or tension) calculated from the ultimate bending moment if the interface is in the tension zone or

the compression from that part of the compression zone above the interface calculated from the ultimate bending moment if the interface is in the compression zone

2917 Average horizontal design shear stress The average horizontal design shear stress is the stress obtained by dividing the design horizontal shear force by the area obtained by multiplying the contact width by the beam length between the point of maximum positive or negative design moment and the point of zero moment

The average horizontal design shear stress should then be distributed in proportion to the vertical design shear force diagram to give the design ultimate horizontal shear stress at any point along the length of the member The design shear stress vh should be less than the appropriate value in Table 28

Table 28 ndash Design ultimate horizontal shear stresses at interface

Precast unit Surface condition

Insitu concrete grade

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

as-cast or as-extruded 04 055 065

brushed screeded or rough-tamped 06 065 075

washed to remove laitance or treated with retarder and cleaned 07 075 080

Nominal links projecting into insitu concrete

Notes 1 The description `as-castrsquo covers those cases where the concrete is placed and vibrated leaving a rough finish The

surface is rougher than would be required for finishes to be applied directly without a further finishing screed but not as rough as would be obtained if tamping brushing or other artificial roughening had taken place

2 The description `as-extrudedrsquo covers those cases in which an open-textured surface is produced direct from an extruding machine

3 The description `brushed screeded or rough-tampedrsquo covers cases where some form of deliberate surface roughening has taken place but not to the extent of exposing the aggregate

4 For structural assessment purposes it may be assumed that the appropriate value of m included in the table is 15

2918 Nominal links Nominal links with a gross sectional area of at least 015 of the contact area should be provided Spacing should not be excessive The spacing of links in T-beam ribs with composite flanges should not exceed the greater of four times the minimum thickness of the insitu concrete or 600 mm Links should be adequately anchored on both sides of the interface

2919 Links in excess of nominal If the horizontal shear stress obtained in accordance with clause 2917 exceeds the value given in Table 28 all the horizontal shear force should be designed to be taken by the reinforcement anchored either side of the interface

The area of steel required Ah (mmsup2m) should be calculated from the following equation

1000 b vhAh = 087 fy

where b is the breadth of the section in mm and

vh is the design shear stress in Nmm2 as defined in clause 2917

29110 Vertical shear (a) General

For composite members resisting vertical shear due to design ultimate loads the design should be in accordance with the Code of Practice for Structural Use of Concrete

(b) Insitu concrete with precast prestressed units

When the composite concrete section is used in the design of such units the design principal tensile stress should not exceed 024fcu anywhere in the prestressed units The stress should be calculated by making due allowance for the construction sequence and by taking 08 times the compressive stress due to prestress at the section considered

29111 Structural topping (a) Thickness

The minimum recommended thickness is 40 mm nominal with a local minimum of 25 mm

(b) Workmanship Workmanship is important to achieve a good shear connection Generally the topping should be well vibrated onto a surface that has been dampened but is free from standing water

Where electrical conduits and the like are to be included within the structure the minimum thickness of topping should be increased accordingly

Under no circumstances should structural topping be used to adjust level differences as a result of erection tolerances thereby resulting in local areas where the thickness is less than the minimum specified above

210 NON-STRUCTURAL ELEMENTS Non-structural precast elements for example faccedilade panels or non-loadbearing partitions whilst not forming part of the structural framing system of a structure will nonetheless be subjected to selfweight and wind loading The elements and their connections should therefore be designed in a similar manner to structural precast elements and in accordance with the relevant sections of clauses 21 to 29 Refer to Appendix B for the typical installation details for precast concrete faccedilade panels

211 DUCTILITY 2111 Construction incorporating precast concrete

When moment resisting frames and structural walls involve precast concrete elements ldquoequivalent monolithicrdquo systems should be adopted

2112 Connections in equivalent monolithic systems Strong connections are to be applied to precast concrete elements of equivalent monolithic systems in moment resisting frames and structural walls strong connections are designed to provide a certain degree of ability to deform beyond elastic limit without excessive strength or stiffness degradation and to ensure that flexural yielding occurs away from the connection region The design should accommodate possible yield penetration into the connection region as in cast-inshyplace construction and to follow the principle adopted in the Code of Practice for Structural Use of Concrete on detailing for ductility

3 CONSTRUCTION

31 PRODUCTION PLANNING Detailed planning at the pre-production stage is essential to ensure a safe and successful manufacturing supply and erection process for a precast concrete system The manufacturing programme and resources must be synchronised so that the delivery rate matches the project construction requirements and available site storage Any special transport requirements or site access limitations that may require deliveries outside normal working hours should be identified at this stage

A lead in time for the fabrication of precasting moulds trial elements and connections details should be allowed for Up to six months may not be an unusual period

Production shop drawings usually prepared by the precasting manufacturer should include all necessary information for the following items

member shapes (elevations and sections) and dimensions sections and details to indicate quantities and position of reinforcement anchors inserts

etc joint and connection details production tolerances handling devices including specifically fabricated lifting beamsframes and strongbacks finishes bearing seats methods for storage lifting and transportation and unique identification location and orientation information which is to be marked on the

32 MOULDS 321 Materials

Several factors should be considered when choosing the material for constructing precast moulds such as repetitive use of the mould economics required surface finish type and quality and the shape complexity of the precast unit Environmental aspects should also be considered when selecting a suitable mould material

The moulds should have adequate stiffness to maintain specified tolerances conforming to shape lines and dimensions as shown in the specification

Due to the complexity of tailor-made steel moulds for precast concrete faccedilade panels it is normally considered economical to produce a single steel mould for the construction of 200 or more panels However other considerations mentioned above may govern the selection of steel for the use as a mould material

The design of steel mould is critical because failure of which may lead to delay in programme and also wastage of precast products if it could not achieve the required workmanship and tolerances Material quality and thicknesses three-dimensional restraints demoulding mechanisms temperature effects are important considerations in designing good moulds

322 Tolerances Precast concrete units can be manufactured to comparatively close tolerances although it should be appreciated that as with insitu concrete some dimensional variations are inevitable Manufacturing tolerances should be specified for overall dimensions thickness bow twist flatness squareness size and location of openings and cast-in items The mould tolerances should be compatible with the construction and erection tolerances specified in the specification in order to achieve an acceptable completed precast product

Repetitive operations such as casting concrete vibration mould stripping and re-erection should not affect the mould dimensions beyond permissible tolerances Regular surveys of the moulds should be made to ensure that they are still within acceptable limits

As good practice it is recommended that full re-checking of moulds for dimensional tolerance compliance be carried out after approximately 100 castings More frequent checking may be advisable

323 Recesses sleeves and boxouts These should be formed from suitable material The shape size and location should be identified on the precast unit shop drawings

324 Mould release agents Both suction and friction can be reduced by the use of high quality mould releasing agents These releasing agents should be of a suitable type that will assist in demoulding of the precast unit without causing discolouration adversely affecting the appearance of the surface finish or reducing the adhesion of subsequent finishes such as tiling Their application and timing control should adhere strictly to the manufacturerrsquos recommendations

33 CAST-IN CONNECTIONS Where bars are provided with threaded ends for bolting or sleeve connection a high degree of accuracy in their location is required Templates should be used to fix threaded bars bolts inserts sleeves and base plates during the production of precast units and cast insitu elements

For complicated connections or connection systems which require very tight construction tolerances mock-up elements should be prepared to ensure any construction difficulties are identified and solved prior to the commencement of mass production of precast units

34 LIFTING INSERTS 341 General

Proprietary lifting inserts should comply with the design requirements of clause 275 Reinforcing bars should only be used as lifting eyes when they have been designed to act in that manner The type of lifting eyes or inserts to be used on a particular project should be agreed between the manufacturer and the contractorerector

Lifting inserts should be firmly fixed to the mould in a manner that prevents them moving out of position during concrete placement Puddling in facelift anchors after pouring of the concrete while it is still in a plastic state is a common and accepted technique Anchors must be cast in at the correct height to accommodate the lifting clutch hook or shackle that will be used to handle and erect the precast element

Recess formers should be well maintained and must be compatible with the type of insert that is to be used

Appendix C shows some good practices on lifting hooks and lifting beams for reference

342 Lifting position tolerances Recommended tolerances on the location of lifting devices for typical precast elements are given in table 31 below

Table 31 ndash Recommended tolerances for lifting devices Type of unit Location on the unit Tolerance

Pile 150 mm

Floor slab 150 mm

Beam Along the length

Across the width

300 mm

Column Along the length

On the end

300 mm

Wall or faccedilade panel

In the face in any direction

On the edge across the thickness

On the edge longitudinally

35 SURFACE FINISHES 351 Types of finishes

Various types of finishes can be produced The more common types are plain (off form) finishes patterned finishes tiled finishes and surface finishes treated by tooling sand blasting or acid etching

Prior to the commencement of mass production of precast units trial units should be prepared so that the surface finish quality can be inspected agreed and approved by all parties concerned Often several adjustments and improvements are necessary before the desired product finish is achieved

352 Production The quality of a concrete surface finish that can be achieved is dependent on the properties and constituents of the concrete mix the type of form material and releasing agent the placing and compaction of the concrete and the measures taken to cure the concrete

353 Tiled finishes Precast panels may have tiling added after casting or frequently where panels are cast flat the tiling can be placed in the mould before the concrete is poured Where tiling is added after the panels are cast a thin bed tile adhesive is commonly used to attach the tiling Any adhesive should be applied strictly in accordance with the manufacturers instructions

Mould releasing agents curing compounds and the like can significantly reduce the adhesive bond between the tiles and the concrete therefore care should be taken to ensure that these substances are removed from the concrete surface before the application of any adhesives

Waterproofing agents are also known to reduce tileconcrete adhesion and if these are present in the concrete specialist advice must be sought

Where tiling is placed directly in the mould to preserve the joint appearance it is sometimes necessary to initially grout up the joints and often a layer of adhesive is then applied to the back of the tiles before pouring the concrete It is however essential that the concrete is placed before the adhesive set commences thereby reducing the bond This period is referred to as open time and is particularly critical when reinforcement has to be placed in the mould after adhesive application and prior to concrete placement

36 PREFABRICATED METAL FRAMES Prefabricated frames such as windows that are to be incorporated into the precast units should be manufactured in accordance with the appropriate standards

As the frame surfaces may be damaged by fresh concrete adequate protection should be provided Where frames are to be cast in fresh concrete the surface in direct contact with the concrete may have a protective coating if recommended by the supplier

Prefabricated frames should be manufactured with suitable lugs on the face that is to be in contact with concrete to ensure proper bonding to the precast unit Frames should be secured in such a way that they cannot move or deform in the mould during concrete placement

37 PRE-CONCRETING CHECK The following items should be checked prior to concreting

overall dimensions squareness of corners and of edges condition of side and base of mould location of cast-in items including starter bars dowels and lifting inserts etc and support location of reinforcement and support concrete cover to reinforcement boxouts for openings provision for finishes

identification and marking windows

38 CONCRETE PLACING Placing and compacting of fresh concrete should be carried out under proper supervision Compaction should be thorough and care should be taken to avoid displacing reinforcement tendon ducts and anchorages and cast-in items and to avoid damage to the faces of the mould

39 DEMOULDING AND LIFTING Precast concrete elements should only be demoulded once the concrete has achieved sufficient strength to withstand the stresses due to the demoulding process and initial handling Strength may be assessed by tests on cubes cured as far as possible under the same conditions as the concrete in the element being considered

The minimum concrete strength at which precast elements can be lifted from the mould will be determined by the magnitude of the greater of the concrete stresses at the lifting points the stresses caused by the transfer of prestressing forces or the stresses from handling

For vertically cast panels or elements cast on tilting moulds the flexural stresses may not always determine minimum concrete strengths required In these situations the minimum strength of the concrete at initial lift may be governed by the required capacity of the lifting inserts

The capacity of lifting inserts may be less than their rated capacity due to short embedment lengths insufficient edge distances andor low concrete strengths at the time of lifting Higher strengths than those recommended in the table below may therefore be required to develop the capacity of some lifting inserts or for safe handling of the elements

Table 32 ndash Recommended minimum concrete strengths for lifting and handling

Application Minimum concrete strength

None specified fine controlled crane non-prestressed 10 Nmm2

Lifting which involves significant impact or high acceleration 15 Nmm2

All units where concrete strength for lifting is specified in the specification as specified

Concentrically prestressed elements (piles wall panels or thin floor slabs) 20 Nmm2

Eccentrically prestressed elements (tees deep flooring units) 25 Nmm2

Bridge beams and similar highly stressed prestressed elements 30 Nmm2 or as specified

Dependent on anchor length or as recommended by insert manufacturer

With prestressed elements special care should be taken to ensure lifting devices are anchored in compression zones unless covered by specific design

Initial lifting should be made cautiously and gradually to overcome suction and friction without inducing sudden impact forces

310 CURING 3101 Normal curing

The method and duration of curing should be such that the concrete will have satisfactory durability and strength and that the precast unit will not distort and will not cause undue cracking due to shrinkage Suitable methods of curing include

delaying mould removal

covering the concrete surface with an impermeable sheet of material such as polyethylene The sheet should be well sealed and fastened spraying the concrete surface with an efficient curing membrane covering the concrete surface with a continuously damp absorbent material or continuous or frequent applications of water to the surface avoiding alternate wetting

and drying or application of cold water to warm concrete surfaces Surfaces should normally be cured for a period of not less than 4 days

3102 Steam curing Once the placement of concrete is complete the concrete must be left for 4 hours without additional heating With steam curing the concrete temperature can then be raised at a maximum rate of 10degC per half hour The concrete temperature should at no time exceed 70 degC and the rate of subsequent cooling should not exceed the rate of heating

Steam curing should be under a suitable enclosure such that the live steam can be retained Steam jets should be positioned to allow free circulation of the steam around the surfaces of the members and to avoid discharge directly onto the concrete or the test cubes

311 HANDLING The handling process encompasses the demoulding of the precast units their loading and transportation to storage areas offloading and storage transfer to site and site erection

To avoid excessive stresses and possible damage all precast units should be handled in the manner as envisaged in their design by means of approved devices identified in the production and erection drawings

The techniques for handling precast units should aim for successful fabrication delivery and installation without causing structural damage detrimental cracking architectural impairment or permanent distortion

312 POST-CONCRETING CHECK 3121 General

The size and shape of the precast units should be checked for compliance with the specification and that they are within specified tolerance limits Other items should also be checked to ensure the units are acceptable for project use They include checking that

connectors sleeves recesses and other features are in their correct location and were not misaligned or dislodged during concreting construction joints have been formed as designed reinforcement protruding from the element is the correct diameter and length and in the

correct location surfaces are free from cracks hollow spot and unevenness and exhibit no signs of grout

loss major chipping or misalignment of joints earthing lugs when required provide full electrical continuity and identification and marking is correctly attached

It may be desirable to instigate 2 stages in the checking works stage 1 immediately after demoulding to identify the repairable and non-repairable

damages The non-repairable elements are to be discarded stage 2 post-repairs and post-finishing when the precast units are ready for dispatch

3122 Surface finish 31221 Inspection

The surface of precast units should be inspected for defects and for the conformity with the specifications The making good of surface defects may be permitted subject to the approval of the

registered structural engineer but the standard of acceptance should be appropriate to the type and quality of the finish specified

31222 Cracks Precast units that have been adequately designed for the stresses due to serviceability effects and handling are generally free from cracks when correctly demoulded transported and handled However sometimes cracks may occur as a result of difficulties in demoulding rough handling concrete shrinkage and improper concrete mix

31223 Repairs Any defects found in a precast unit should be checked to ensure that the unit is still aesthetically and structurally acceptable for use after an appropriate repair is made

The type of repair material and method depends on the pattern extent of the defect and type of surface finish and should be agreed by all parties involved and approved by the registered structural engineer The repair materials and method should be effective and acceptable in terms of achieving the required concrete strength and structural integrity as well as producing a texture and colour similar in appearance to the surrounding surface

313 LIFTING EQUIPMENT AND ACCESSORIES Lifting equipment such as mobile crane gantry crane forklift etc must be carefully selected to ensure that lifting of precast units is carried out within the rated capacity of the equipment The support for the lifting equipment must be checked to ensure that adequate supporting capacity is provided

Lifting accessories may comprise combinations of lifting beams or frames slings or cables hooks or shackles The selection of each of these components should be predetermined to take account of the forces exerted on them due to all aspects of the lifting operations A person suitably qualified in accordance with the relevant regulations must regularly inspect all lifting equipment prior to and after use Results of such inspections must be properly recorded and be available for subsequent inspection by the registered structural engineer upon request

Some precast elements such as prestressed hollow-core floor slabs must be handled by means of lifting clamps strops or slings as they may have no lifting inserts Lifting equipment of this type may wear rapidly and therefore should be regularly inspected The location of lifting points should be clearly indicated on the drawings

314 FACTORY AND SITE STORAGE Storage areas must be large enough so that the precast units can be stored safely with adequate room for lifting equipment and transporting vehicles to manoeuvre The ground of the storage area must be hard level clean and well drained to permit organised storage

Precast elements can be damaged by incorrect stacking and storage Where the locations of support points for a precast unit are critical the locations for the supports (dunnage) should be noted on the shop drawings

Supports must be arranged to avoid twisting or distorting of the precast elements and must be adequate to transfer the weight of the stacked units to the ground without excessive settlement

The stored and stacked units should be protected to prevent accidental damage and discolouration and the support material should be non-staining Lifting points should also be well protected and kept accessible while the units are in storage

Precast units must be stored safely with adequate supports such that it would not endanger any workers moving in the vicinity

315 TRANSPORTATION 3151 Delivery

Commonly precasting factories lie outside the Hong Kong SAR in Guangdong province China and in order to get the products to the construction site it is necessary for road andor water transportation

For transportation within China regional authority transportation requirements will need to be met and permits where applicable obtained Within the Hong Kong SAR transportation must comply with the appropriate regulations

The precast units should have gained sufficient strength before being loaded for transportation

3152 Loading and storage on transporters Precast units must be loaded carefully on to delivery vehicles to prevent damage To protect the edges throughout their journey proper devices should be used to support secure and wedge the precast units The units should be adequately secured and supported to prevent them from overturning shifting or being damaged during transportation Adequate non-staining cushioning should be provided between the unit and any securing chains cables or ropes to prevent localised damage

Precautions should also be taken to ensure that no undesirable stresses will be transmitted to the precast unit due to any flexing of truck or barge deck

316 ERECTION 3161 Erection preparation

Consideration should be given to the following items to ensure safe and efficient installation of the precast elements in accordance with the design intent

erection sequence assembly and erection method erection tolerances rigging requirements concrete strength or age requirements permanent structural connection and joint details and propping and temporary support details

If the sequence of erection is critical to the structural stability of the structure or for access to connections at certain locations it should be noted on the drawings The erection drawings which should include all relevant information should be prepared prior to the commencement of any erection

3162 Erection safety Safety during the handling and erection of precast concrete elements is of paramount importance and compliance with the relevant current regulations is required

All equipment used for the handling and erection of a precast element must be maintained to a high standard load tested as necessary and be suited to the intended use

Consideration should also be given to the site environment particularly with regards to built up areas and implications this may have on erection safety

3163 Erection sequence Precast elements should be erected in accordance with a pre-planned sequence as detailed in the erection drawings This sequence of erection should be such that the multiple handling of elements is minimised A trial erection operation should be considered to identify any unforeseen erection difficulties

3164 Missing or damaged lifting inserts If missing faulty or incorrectly located lifting inserts are identified the designer should be contacted immediately to assess the problem and decide on an alternative lifting system

It should be verified where permanent fixings or connections are temporarily used during construction that the fixings are suitable for the temporary use and their long-term performance will not be compromised

3165 Rigging A rigging system for handling and erecting precast elements requires careful and thorough preshyplanning Special care must be taken with rigging arrangements where unequal lifting loading has been incorporated in the panel design

It may be necessary to check the centre of gravity during lifting in order to ensure a stable and balance manner to facilitate installation operation

The loadings at different lifting points may be different It is common to use chain slings for lifting Careful design the required length of the chain slings for different lifting points to ensure proper tightening and no slack during lifting operation

Refer to Appendix C for details of lifting hook for semi-precast slab and typical lifting beam for precast faccedilade

3166 Temporary bracing and supporting structures Precast concrete elements must be adequately braced and supported during all phases of erection to ensure proper alignment and structural integrity until permanent structural connections have been completed

The design of temporary bracing and supporting structures should comply with clause 276 The installation and erection is to be in accordance with the approved drawings and checked by a competent person as set out in the projectrsquos Site Safety Supervision Plan

Wherever possible bracing should be fixed to the element before lifting When it is necessary to attach the braces after the element has been positioned the element should not be detached from the crane until the braces have been installed

Bracing bolts should be checked at regular intervals to ensure that they are secure and undamaged

3167 Levelling shims Levelling shims should be formed from a suitably durable material and should have adequate strength to carry the full imposed loads Direct concrete to concrete or concrete to steel bearing should be avoided

Levelling shims carry the full construction load of the precast element and must provide adequate support to prevent movement until the element is incorporated in the main structure Levelling shims must therefore be used on a solid foundation It is recommended that levelling shims are not placed on thin layers of site concrete

Shimming should not exceed a height of 30 mm unless steps are taken to ensure stability of the temporary support

Where possible shims for levelling precast elements should be located at least 300 mm from the ends of the element This is relevant where edge break-out can occur if shims are placed close to bottom corners such as for thin wall panels

If steel shims are used they must be removed before the final grouting up of the joint

3168 Propping All temporary propping requirements must be shown on the erection drawings The design of temporary propping systems should be in accordance with clause 274 Consideration should be given to the following

propping that supports beams should accommodate possible changes to the distribution of loads during the construction process the seating of precast beams may not be adequate to transfer high loads during

construction and precast beams will normally require full propping at each end if the structural design requires beams to be supported without the use of mid-span

props (to reduce the end support dead load bending moments) this requirement must be clearly noted on both the contract drawings and the precast layout drawings

where beams have floor systems placed on them prior to the beams being fully built into the structure the beams may not be evenly loaded by the floor units during construction Long span floor units placed on one side only of a beam may cause the beam to roll on the props In such circumstances each edge of the beam may require separate temporary propping all temporary propping should be in place adjusted to the correct levels allowing for any

required cambers and fully braced prior to commencement of erection of any precast beams unless specific provision has been made to do otherwise temporary propping should provide full support for all construction loads including the full

self weight of the completed floor system and possible local concentrations of load during construction unless specifically noted otherwise required duration of propping time and sequence of de-propping all temporary propping should be in place adjusted to the correct levels allowing for any

required cambers and fully braced prior to commencement of erection of any floor units unless specifically noted otherwise and props should be vertical and braced to prevent side-sway of the whole assembly and the

buckling of individual props 3169 Cleansing to semi-precast slab

Cleansing and crack inspection before placing insitu concrete topping includeshy

(1) Remove all laitance loose materials dirt and grease from the top surface of the precast slab by using water jet with a minimum pressure of 10000kPa (100bar) for cleansing

(2) After water-jet cleansing check for cracks at the underside of the semi-precast slab (3) Repair any through cracks identified before placing insitu concrete topping to the semishy

precast slabs

317 TOLERANCES

The tolerances which can be achieved in practice depend on a number of factors including

(1) unit shape particularly the effect on the stiffness of the mould (2) mould materials and the method of mould assembly (3) number of castings from each mould (4) position and shape of any projections and (5) method of installation

Production and erection tolerances are given below as a general guide to the accuracy that can be achieved by normal production methods In any case the final construction tolerance of precast concrete construction should not more than the construction tolerances stated in the Code of Practice for Structural Use of Concrete (ie Construction Tolerance ge Production Tolerance + Erection Tolerance)

3171 Production tolerance for precast concrete components 31711 All elements (unless otherwise specified)

1 Length up to 2000 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipplusmn6 mm 2 Width or height up to 250 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn4 mm 3 Thickness or depth up to 500 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipplusmn6 mm

31712 Faccedilade and wall units

(a) Deviations from Design Dimensions

Manufacture the facade and precast concrete wall units within the dimensional tolerances set out below

1 Length and height a Up to 2 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn3 mm b 2 m to 3 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn6 mm c 3 m to 45 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn9 mm d 45 m to 6 m or more helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip +10 mm -12 mm

2 Thickness a Up to 500 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip +6 mm -3 mm b 500 mm to 750 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip+8 mm -5 mm

3 Straightness or bow (deviation from intended line) a Up to 3 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 6 mm b 3 m to 6 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 9 mm c 6 m to 12 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip12 mm

(b) Squareness

When assessing the squareness of a corner

1 Take the longer of the two adjacent sides being checked as the base-line

2 Ensure that the shorter side does not vary in its distance from a perpendicular so that the difference between the greatest and shortest dimensions exceeds Length of shorter side a Up to and including 1000 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 3 mm b Over 1000 mm to 2000 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 5 mm c Over 2000 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 6 mm

(c) Twist

Ensure that no corner is more than the dimension stated from the plane containing the other three corners

1 Up to and including 3m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 6 mm 2 Over 3m to 6m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 9 mm 3 Over 6m to 12m helliphelliphelliphelliphelliphelliphelliphellip 12 mm

(d) Position of Cast-in Window Frames

Permissible deviation from design dimensions on plan helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn6 mm

3172 Erection tolerance for precast concrete components 31721 All elements (unless otherwise specified)

After erection of the precast component the construction tolerance shall well within the construction tolerances stipulated in Code of Practice for Structural Use of Concrete

31722 Precast faccedilade and precast wall units

Install the facade and precast concrete wall units within the erection tolerances set out below

1 Position on plan In x and y directions helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn5 mm

2 Verticality per element helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn6 mm

3 Width of joint On a nominal joint of 20 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn5 mm

a In addition respect the prescribed dimensions for height width and length of the completed building to within 01

b Respect the theoretical line both horizontal and vertical with the same tolerance of 01 for each storey when seen from the front Deviations in profile must not exceed plusmn10 mm

31723 Stairs (flight from landing to landing)

(a) Position on Plan

Permissible deviation on plan of any point in relation to the nearest reference point at the same level the distance between the points being not more than 15m helliphelliphelliphelliphelliphelliphellipplusmn10mm

(b) Length

Length on plan of clear span (excluding landings) helliphelliphelliphelliphelliphelliphelliphelliphelliphellipplusmn12 mm

(c) Width of Flight helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn6 mm

(d) Height

Vertical height measured between either top surfaces or soffit surfaces of any flight of stairs helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn10 mm

(e) Waist Thickness

Thickness of waist measured at right angles to the slope of the flight +6 mm -3 mm

(f) Rise

Difference in the rise of two consecutive steps helliphelliphelliphelliphelliphellip plusmn5 mm

(g) Going

Difference in width of tread of two consecutive steps helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn8 mm

(h) Tread Level

Difference in level of tread

1 Across the going helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn4 mm 2 Across width of stair helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn5 mm

3173 Volumetric precast concrete components 31731 Position on Plan

Permissible deviation on plan of any point measured f rom the nearest building grid line helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn15 mm

31732 Length and Width

a le15 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn25 mm b gt15 m le30 mhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn25 mm c Each subsequent 30 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipplusmn20 mm

Note Measure dimensions at lowest floor level or if not practicable as otherwise specified or agreed

31733 Height

To structural roof level with reference to the Transferred Bench Mark (TBM)

le30 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn40 mm Each subsequent 30 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn15 mm

31734 Verticality of Wall and Columns

a b cd

Plumbness in height le500 mmhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn10 mm Ditto gt500 mm le3000 mm helliphelliphelliphelliphelliphellipplusmn15 mm

Ditto gt3000 mm le30 m helliphelliphelliphelliphelliphelliphellip plusmn20 mm gt30 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip Pro-rata on plusmn20 mm per 30 m to the nearest 5 mm

Note When separated by another plane or member use the thickness of the plane or member for checking verticality

31735 Surface Profile of Walls and Slab Soffits

Permissible deviation from mean of surface profile across the whole element (from extremities)

a Surface profile le3000 mmhelliphelliphelliphelliphellip plusmn10 mm b Ditto gt3000 mm le15 mhelliphelliphelliphelliphelliphellip plusmn15 mm c Ditto gt15 m helliphelliphelliphelliphelliphelliphelliphelliphellip plusmn20 mm

Note Measure deviations in two directions

31736 Twist

The distance of any one corner from the plane containing the other three corners ie a variation from the target plane

a For diagonal le15 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 20 mm b For each further 10 m of diagonal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 10 mm

31737 Squareness of Corners

Where the longer of two adjacent sides is taken as the base line and the permissible deviation of the shorter side from a perpendicular to the base line is related to the length of the shorter side

a Short side le3000 mm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipplusmn20 mm b Short side for every additional 2500 mm (to nearest 5 mm) helliphelliphelliphelliphelliphelliphelliphelliphellip20 mm x L3

31738 Level

Permissible deviation from designed level with reference to the nearest Transferred Bench Mark (TBM) of the upper or lower surface as may be specified of any slab or other element or component

a Length le8 mhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn10 mm b Length gt8 m le15 m helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn15 mm c Length gt15 m le30 mhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip plusmn20 mm

4 QUALITY CONTROL 41 FACTORY 411 General

A factory selected for the casting of units must ensure that the precast units are manufactured under a Quality Assurance Scheme certified under ISO 9001 covering the following items

quality control tests of materials including proprietary products such as lifting anchors for handling precast concrete components

calibration of laboratory equipment for quality control tests production process efficiency and proper operation of equipment at the casting yard samplingtesting procedures and requirements frequency and extent of inspection by in-house staff and independent parties and frequency and extent of audit by in-house staff and independent parties

The factory and contractor are responsible for maintaining the quality of the manufacturing process for the precast units The precast concrete elements should be manufactured by a factory with ISO 9001 quality assurance certification The contractor should provide continuous supervision of the precast concrete production works in the factory as well as qualified supervision for the fabrication erection and examination of precast concrete elements

The authorised personregistered structural engineer must satisfy himself that the precast concrete units have been constructed in accordance with the approved drawings and specification The registered structural engineer and his team of supervisory personnel should provide qualified supervision for the fabrication erection and examination of precast concrete elements Should more stringent control be considered necessary the authorized personregistered structural engineer may step up the supervisory and testing requirements

Rigorous quality control procedures must be maintained at the precasting factory at all times to ensure that the precast elements are constructed in accordance with the Building (Construction) Regulations and specification

Upon leaving the precasting factory all precast units or batch of units must carry documentation certified by the factory stating that the units have been manufactured under a certified Quality Assurance Scheme and in accordance with the specification

Precast units produced and handled by a quality assured factory shall be fully traceable Serial number casting date concrete grade reinforcement details final locations and delivery order invoice should be documented The date of manufacture together with the serial number shall be marked on each precast unit Manufacturer may install radio frequency identification (RFID) tags to the respective precast unit to record the manufacturing process the logistics in delivery and the installation details of the precast unit etc

Clauses 32 and 39 provide guidelines in respect of quality control on moulds demoulding and lifting respectively Reference shall be made to clauses 311 and 314 for quality control on handling andor storage of cast units

412 Testing standards 4121 Concrete

Sampling and testing of concrete should comply with the Building (Construction) Regulations and as required by the specification in accordance with Construction Standard CS1 or similar approved The testing is to be undertaken by a laboratory accredited under the Hong Kong Laboratory Accreditation Scheme (HOKLAS) or other laboratory accreditation bodies which have reached mutual recognition agreementsarrangements with the HOKLAS

4122 Reinforcement Sampling and testing of reinforcement should comply with the Building (Construction) Regulations and in accordance with Construction Standard CS2 or similar approved The testing is to be undertaken by a laboratory accredited under HOKLAS or other laboratory accreditation bodies which have reached mutual recognition agreementsarrangements with the HOKLAS

4123 Structural Grouting All grout should be prepared applied in accordance with the manufacturerrsquos specification and requirements and tested in accordance with Construction Standard CS1 by a laboratory accredited under HOKLAS or other laboratory accreditation bodies which have reached mutual recognition agreementsarrangements with the HOKLAS The strength of 100 mm cubes of grout must not be less than the grade strength of the adjoining concrete

42 SITE Receiving lifting storage and erection at the construction site should be undertaken in accordance with an accredited site Quality Assurance Scheme

The following items should form part of the site checking for acceptance of the precast elements

Structural integrity Although quality control checks are carried out for the precast units at the factory there is a possibility of damage during handling and transportation As the precast units are received on site they should be visually inspected for any signs of structural defect

Dimensional tolerance Dimensional tolerances of the precast units as received on site should comply with the specification See clause 317 for guidance on production tolerances

Changes to the dimensions and shapes of units should be identified and assessed with regard to the overall tolerance and

Surface finish The surface finishes of precast units when received on site should be checked for compliance with the requirements of the specification

43 SPECIAL TESTING 431 Watertightness testing of external precast faccedilade panels 4311 General

For facade units not connected monolithically to in-situ concrete it is required to demonstrate that the joints are adequate to resist water penetration Water penetration test on a full scale mock-up panel including joint could be undertaken The recommended testing procedure is outlined in clauses 4312 to 4315

4312 Test procedures Mock-up panels to be tested for watertightness should be subjected to both static and cyclic pressure in accordance with relevant international standards [eg ASTM E331-00 (2009) and ASTM E547-00(2009) respectively] These testing procedures are to be modified for local conditions as follow

differential test pressure shall be 20 of the maximum inward design wind load but not less than 077 kPa and

the test shall be performed with water flow rate of 34 litresminmsup2 for 15 minutes

4313 Sampling for water penetration test Full scale watertightness testing on precast faccedilade panels and joints should be carried out at the rate of 05 for each type of joint and combination of panels or one for each type of joint and precast unit whichever is the greater

4314 Failure criterion The faccedilade units or joints are deemed to have failed if signs of water seepage through the joints or through the faccedilade unit including signs of damp patches are observed during the test or within the subsequent 2 hours after the test

4315 Remedial action Upon failure of a water penetration test on a precast faccedilade system the cause of failure should be identified and the system revised and re-tested until a satisfactory test result is achieved

For any one facade unit fails the watertightness test additional tests shall be required with sampling rate determined by the registered structural engineer

432 Load testing When supervision indicates poor workmanship or where there are visible defects particularly at critical sections tests to determine the structural integrity concrete strength and quality of materials may be carried out to determine the acceptability of the product or the batch of products The testing method should be specific and capable of collecting relevant information to verify the acceptability of the product

In certain cases it may be necessary to devise specific tests to demonstrate the structural integrity of the precast unit In this circumstance such testing method should be relevant and agreed with the registered structural engineer prior to conducting the test

433 Tiled finishes Performance testing should be carried out on a number of trial panels at the precasting yard to demonstrate the method and materials used for fixing the tiles will be satisfactory in service

There should be no hollow sounding areas behind the tiles when the surface is tapped with a light hammer or coin

Pull off tests may be required on selected areas of tiling

A cover meter survey of reinforcement beneath the tiled finish should be made to ensure adequate cover to reinforcement has been provided

The number of trial panels the number and nature of tests and the acceptance values should be specified and agreed before manufacture

Acceptance testing on production panels should be carried out at an appropriate time to avoid the erection of panels with unacceptable finishes Any of the recommended testing may be employed but it should be noted that pull off testing is destructive and the tested area cannot easily be repaired to the original appearance

Reference

This Code of Practice incorporates provisions specified in the following documents These documents are referred to at the appropriate parts of the text For dated references if any subsequent amendments or revisions do not apply For undated references the latest edition of the publication applies

Hong Kong Building (Construction) Regulations

Code of Practice for Structural Use of Concrete 2013

Code of Practice for Fire Safety in Building 2011

Structures Design Manual for Highways and Railways

Code of Practice on Wind Effects in Hong Kong 2004

Code of Practice for Dead and Imposed Loads 2011

結構書籤

Code of Practice for Precast Concrete Construction

Code of Practice

FOREWORD

CONTENTS

1 General1

11 Scope 1

12 Definitions 1

13 Symbols 2

2 Design 3

21 Scope 3

22 Planning 3

23 Stability 4

24 Durability 5

25 Loadings 6

26 Materials 7

291 General 26

211 Ductility 28

3 Construction 29

32 Moulds 29

310 Curing 32

311 Handling 33

316 Erection 35

317 Tolerances 37

41 Factory 41

42 Site 42

LIST OF TABLES

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

FOREWORD

CONTENTS

1 General1

11 Scope 1

12 Definitions 1

13 Symbols 2

2 Design 3

21 Scope 3

22 Planning 3

23 Stability 4

24 Durability 5

25 Loadings 6

26 Materials 7

291 General 26

211 Ductility 28

3 Construction 29

32 Moulds 29

310 Curing 32

311 Handling 33

316 Erection 35

317 Tolerances 37

41 Factory 41

42 Site 42

LIST OF TABLES

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

CONTENTS

1 General1

11 Scope 1

12 Definitions 1

13 Symbols 2

2 Design 3

21 Scope 3

22 Planning 3

23 Stability 4

24 Durability 5

25 Loadings 6

26 Materials 7

291 General 26

211 Ductility 28

3 Construction 29

32 Moulds 29

310 Curing 32

311 Handling 33

316 Erection 35

317 Tolerances 37

41 Factory 41

42 Site 42

LIST OF TABLES

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

211 Ductility 28

3 Construction 29

32 Moulds 29

310 Curing 32

311 Handling 33

316 Erection 35

317 Tolerances 37

41 Factory 41

42 Site 42

LIST OF TABLES

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

41 Factory 41

42 Site 42

LIST OF TABLES

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

LIST OF TABLES

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

123 4 56 78

LIST OF FIGURES

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

1 GENERAL

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

2 DESIGN

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Product type Finish

Stage Load factor

Yard handling 12

Transportation 15

combination

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

252 and 253)

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Bracing members 2

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

T = 10F

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(see clause 317)

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Steel 0

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Functions

(c) Properties

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

25 (Nmmsup2)

30 (Nmmsup2)

40 and over

(Nmmsup2)

No links

1000 b vhAh = 087 fy

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

3 CONSTRUCTION

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Pile 150 mm

Floor slab 150 mm

Across the width

300 mm

On the end

300 mm

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

precast slabs

317 TOLERANCES

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Squareness

(c) Twist

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

(b) Length

(d) Height

(e) Waist Thickness

(f) Rise

(g) Going

(h) Tread Level

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

31733 Height

a b cd

31736 Twist

31738 Level

Reference

結構書籤

Reference

結構書籤

Reference

結構書籤

Reference

結構書籤

Reference

結構書籤

Documents

Code of Practice for Precast Concrete Contruction 2016 · This Code, Code of Practice for Precast Concrete Construction 2016 (the 2016 Code) is issued upon completion of the review